1. Field of the Invention
The present invention is directed generally to steam turbines, and more specifically to steam turbines of the type employing "axial entry, integral shroud" blades. The present invention has particular application to axial entry, integral blades having a generally fir-tree shaped root, but is not limited thereto.
2. Description of the Prior Art
Steam turbines of the type employing "axial entry, integral shroud" blades comprise a rotor having a plurality of generally fir-tree shaped generally axially-extending grooves, with the blades circularly disposed therearound. Each blade has a generally fir-tree shaped root at a proximal end thereof in registration with one of the grooves and a shroud integral with the blade at a distal end thereof. As is known, blade "flop" may occur during turning gear operation of the turbine, i.e. the blade root may rock circumferentially in the groove with which it registers during turning gear operation because the centrifugal force is insufficient to urge the root radially outward. Blade flop may cause root/groove fretting. Additionally, gaps between adjacent shrouds may open under hot rotor conditions and contribute to blade flop. Moreover, the mating faces of adjacent shrouds may wear from snubbing. Obviously, these are undesirable conditions.